Serum starvation induces cytosolic DNA trafficking via exosome and autophagy-lysosome pathway in microglia

The imbalance of microglial homeostasis is highly associated with age-related neurological diseases, where cytosolic endogenous DNA is also likely to be found. However, the intracellular trafficking of endogenous DNA remains unidentified. In this study, we demonstrated that nuclear DNA (nDNA) and mitochondrial DNA (mtDNA) undergo different intracellular trafficking under conditions of microglial homeostasis imbalance induced by serum starvation. Upon detecting various components of endogenous DNA in the cytoplasmic and extracellular microglia, we found that cytosolic nDNA primarily exists in a free form and undergoes degradation through the autophagy-lysosome pathway. In contrast, cytosolic mtDNA predominantly exists in a membrane-wrapped form and is trafficked through both exosome and autophagy-lysosome pathways, which are key components of intracellular biomolecule trafficking. When the autophagy-lysosome pathway was inhibited, there was an increase in exosomes. More importantly, the inhibition of the autophagy-lysosome pathway resulted in enhanced trafficking of mtDNA through the exosome pathway. These findings unveiled the crosstalk between these two pathways in the trafficking of microglial cytosolic DNA and thus provide new insights into intervening in age-related neurological diseases.